Yes indeed that was one idea a few years back known as extra security but I rarely saw it on my jobs. Other installers often stuck with their own codings throughout installations and from one install to another . Many had similar, if not the same scheme.

The reason I asked the question is that I often found two schools of thought. This depended largely on whether the installer started as a 4 wire person or a 6 wire person although some of the 4 wirers changed as they became six wirers over the years.

Here is what I observed:-

Before the advent of PIRs etc it was basically 4 wire. Two loops. One alarm loop for contacts etc and one antitamper loop  . All using normally closed devices such as door contacts (magnetic reed switches) or microswitches. 

However pressure mats were normally open devices and were wired to join the two loops together when stood upon.

Two pairs of colours were selected for A alarm and B antitamper functions. Often Red and Black were chosen as one loop because they were both single phase and DC colours?

Progress to PIRs and an extra two colours were present and they were then used for +ve & -ve supplies to the PIR detector.

Some installers stayed with that preference but a few changed.

Installers coming up thru the PIRs route often started with Red & Black for +ve and -ve supplies respectively then chose the remaining 4 conductors for their two loop approach.

Off course they might be joined to 8 core, 12 core or even 20 core. I have not seen 20 core for many years though. 

I`m sure that many installers will agree with something broadly similar to what I`ve said but then again I suspect that many might disagree too.

In many cases the two loop system was replace with ID “Biscuits” then Zone resistors both of which freeing up some conductors for other uses and increasing security. Then wireless and icloud based systems.

Yes indeed that was one idea a few years back known as extra security but I rarely saw it on my jobs. Other installers often stuck with their own codings throughout installations and from one install to another . Many had similar, if not the same scheme.

The reason I asked the question is that I often found two schools of thought. This depended largely on whether the installer started as a 4 wire person or a 6 wire person although some of the 4 wirers changed as they became six wirers over the years.

Here is what I observed:-

Before the advent of PIRs etc it was basically 4 wire. Two loops. One alarm loop for contacts etc and one antitamper loop  . All using normally closed devices such as door contacts (magnetic reed switches) or microswitches. 

However pressure mats were normally open devices and were wired to join the two loops together when stood upon.

Two pairs of colours were selected for A alarm and B antitamper functions. Often Red and Black were chosen as one loop because they were both single phase and DC colours?

Progress to PIRs and an extra two colours were present and they were then used for +ve & -ve supplies to the PIR detector.

Some installers stayed with that preference but a few changed.

Installers coming up thru the PIRs route often started with Red & Black for +ve and -ve supplies respectively then chose the remaining 4 conductors for their two loop approach.

Off course they might be joined to 8 core, 12 core or even 20 core. I have not seen 20 core for many years though. 

I`m sure that many installers will agree with something broadly similar to what I`ve said but then again I suspect that many might disagree too.

In many cases the two loop system was replace with ID “Biscuits” then Zone resistors both of which freeing up some conductors for other uses and increasing security. Then wireless and icloud based systems.